Printing machines

ABSTRACT

A printing apparatus having a sheet registering device in which the leading edge of a sheet to be printed upon is allotted a first position. From said position the sheet is arranged to be moved slightly rearwardly by a first abutment means to a second position or a register position. The leading edge is arranged to be held against a support surface by one or more holding-down means, having respective free ends which are arranged to register with or to extend beyond the leading edge of the sheet when said sheet is located in said first position. The abutment means is arranged to move the holding-down means and the leading edge of said sheet to said register position.

United States Patent [191 [111 3,910,569

Ericsson 1 5] Oct. 7, 1975 PRINTING MACHINES [76] Inventor: Sylve Jack Donald Ericsson, Branta Primary [hammer-Even B l unk B v Asszstant Exammer--Robert Satfer acken l7 147 O0 Tumba, SW Attorney, Agent, or FzrmBurns, Doane, Swecker &

eden Mathis [22] Filed: July 25, 1974 [21] Appl. No.: 491,955 ABSTRACT A printing apparatus having a sheet registering device 30 F A P t in which the leading edge of a sheet to be printed orelgn pp Ion "on y Da 3 upon is allotted a first position. From said position the Aug. 13, 1973 Sweden 73110 28 Sheet is arranged to be moved Slightly rearward), by a first abutment means to a second position or a register 27104362211552 position. The leading edge is arranged to be held against a Support surface by one or more holding [58] new of Search 2 down means, having respective free ends which are 2 101/ 410 arranged to register with or to extend beyond the leading edge of the sheet when said sheet is located in said [56] References C'ted first position. The abutment means is arranged to UNITED STATES PATENTS move the holding-down means and the leading edge of 1,250,236 12/1917 Smith 271/244 said sheet to said register position. 2,262,631 11/1941 Belluche 271/243 2,309,662 2/1943 Neuhart 271/243 9 Clams 7 D'awmg F'gures U.S.- Patent Oct.7,1975 3,910,569

PRINTING MACHINES FIELD OF THE INVENTION The present invention relates to a printing machine having a sheet-registering device. In accordancewith the invention, the sheet-registering device may be used with any one of a number of different types of printing machine, although in the following the device will be described solely with reference to a printing machine having a cylindrical printing surface, i.e. a drum printing machine with which the drum is moved forwards and backwards by drive means. These drive means do not form part of the invention.

OBJECTS OF THE INVENTION The invention can be used to advantage with that type of printing machine with which :the sheet to be printed upon, hereinafter referred to as the sheet, is advanced to a first position and from there to a second position which constitutes the so-called register position. When advancing the sheet to the first position, it is normal practice to cause said sheet to be fed against a first abutment. The leading edge of the sheet is intended to engage the first abutment thereby to roughly align the sheet in the printing apparatus. Normally, when the leading edge of the sheet engages the first abutment it is passed beyond the second position or register position, and it is therefore necessary to move the sheet rearwardly so that said leading edge is at said second or register position. This is most suitably achieved by providing the drum with second abutments. These second aubtments are arranged to move the sheet slightly rearwardly to the register position and, immediately the sheet occupies said register position, gripping devices are arranged to hold the sheet firmly during a printing sequence or part of said sequence.

With this arrangement, however, the sheet can only be reliably moved to said second or register position if said sheet comprises a rigid material. When the sheet comprises a thin relatively flexible material, errors may occur when positioning said sheet in the register position. The reason for such errors is that the leading edge of a thin sheet is not able to take up those forces required to move the whole sheet rearwardly to the second or register position without said leading edge being folded up against the second abutment. Thus, a thin sheet will adopt substantially the same position as that occupied by said sheet when it engages the first abutment. Admittedly the difference is only of the order of some few mm., but this is sufficient to create problems, particularly with respect to multicolour printing processes. The expedient of extending the second abutment so that said abutment extends across the whole width of the sheet would give rise to problems of construction and neither would it produce the desired effect.

An object of the present invention is to provide ways and means by which the aforementioned disadvantage can be at least substantially reduced and to enable a sheet to be moved so that the leading edge of said sheet occupies the register position even if said sheet should be extremely thin. H

Accordingly this invention consists in a printing machine having a sheet-registering device, in which the leading edge of the sheet is allotted a position from which the sheet is moved slightly rearwardly by an abutment means to a second position or a register position, wherein said leading edge is arranged to be held against a supportingsurface by one or more holdingdown means having free ends which are intended to register with or to extend beyond the leading edge of said sheet when said sheet occupies said first position, and wherein said abutment means is arranged to move the holder-down means and the leading edge of the sheet to said register position.

BRIEF DESCRIPTION OF THE DRAWINGS So that the invention will be more readily understood and further features thereof made apparent, two proposed embodiments will now be described with reference to the accompanying drawing, in which:

FIG. 1 shows diagrammatically the registering of the leading edge of a sheet in a previously known printing machine;

FIG. 2 shows diagrammatically the registering of the leading edge of a sheet in a printing apparatus constructed in accordance with the invention, said apparatus being provided with a first embodiment of a holding-down means according to the invention;

FIG. 3 shows the holding-down means and the leading edge of said sheet in the register position;

FIG. 4 shows a situation in which gripping means hold the sheet firmly against a printing surface;

FIG. 5 shows diagrammatically and in perspective a drum printing machine in the position shown in FIG. 2;

FIG. 6 is a side view taken partly in section through the line VI-VI in FIG. 5; and

FIG. 7 is a side view of a second embodiment of a holding down means according to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENTS The invention will be described in detail with reference to the accompanying drawings, as applied to a printing apparatus having a cylindrical printing surface. The cylindrical printing surface is arranged to be moved reciprocatingly by means of a drive means (not shown). The printing apparatus referred to will normally operate with a silk-screen frame which is arranged for horizontal reciprocating movement in response to rotation of the cylinder. The apparatus also comprises a squeegee,an ink-applying device. For the sake of clarity, however, the frame, the squeegee, and

the ink-applying device have not been shown in .the drawing.

FIG. 1 is an extremely simplified side view of a known sheet-registering device. The register position has been indicated by reference R and with the position shown in FIG. 1, the leading edge la (FIG. 2) of the sheet 1 has been permitted to pass beyond the register position R. It sufficies here that the sheet 1 obtains a rough alignment, which can be effected in a number of ways and by means of a number of different devices. With the illustrated embodiment, this alignment of the sheet in said first position is achieved by bringing the leading edge 1a of sheet 1 into abutment with the sur face 21: of a first abutment means 2, upon rotation of the drum or cylinder 4. The leading edge In of said sheet is now to be moved from said first position rearwardly to a second or register position R, by means of a second abutment means 3. The second abutment means 3 is mounted on the printing cylinder 4 and upon further displacement or rotation of said cylinder in the directionof arrow (1, the abutment means 3 will engage the leading edge la of sheet 1 in the first position, thereby moving the sheet 1 as a whole rearwardly to the second position, so that said leading edge la is located exactly in the register position R. With the sheet in the register position, gripping means, FIG. 4, are arranged to hold the sheet 1 against the printing cylinder 4, whereupon the printing sequence can be started, by causing the cylinder 4 to be rotated in the direction shown by arrow b. As will be seen from FIG. 5, it is a prerequisite to the operation of this arrangement that the second abutment 3 shall engage the leading edge 1a of the sheet to one side of the first abutment 2, since said first abutment is securely connected to the frame.

In order for the sheet 1 to be reliably moved from the first position slightly rearwardly to the register position R, it is necessary for the sheet 1 to have such a rigidity that said sheet can be moved rearwardly solely by means of the abutment 3 without buckling, said abutment being arranged to engage part of the leading edge la of said sheet. If the sheet has insufficient mechanical strength (i.e. is too thin) the abutment 3 may be unable to move the sheet back to the register position without the leading edge la of said sheet bending up against the abutment 3. This means that the sheet 1 will not be located in the register position, but will remain in the first position in which it abuts the first abutment means 2, as illustrated in FIG. 1. Even though the distance between the register position and the second position R shown in FIG. 1 is only I to 2 mm., it will be obvious that such misalignment of the sheet will create serious problems, particularly with respect to multi-color printing processes.

To facilitate correct alignment of the sheet in the register position R there is provided with the printing apparatus according to the invention a device 5, the function of which will be described with reference to FIGS. 2-4. In FIGS. 2-4 the first abutment means 2 has been omitted, while in FIGS. 2 and 3 the gripping means 6 has also been omitted, for the sake of clarity.

In FIG. 2, the sheet 1 is shown with its leading edge In in the first position, i.e. the position shown in FIG. 1 in which the leading edge la engages the first abutment 2. The device according to the invention is suitably connected to one end thereof to an appropriate fixture and is arranged to bear against the leading edge 1a of sheet 1 to force said edge against a supporting surface, in this case the printing cylinder 4. The other free end 5a of the device 5 is intended to extend slightly beyond the leading edge la of said sheet 1 when said leading edge is located in the first position and abuts the abutment means 2. The free end of the device 5, however, may be arranged to terminate flush with the leading edge la. Since the purpose of the device 5 is to hold the leading edge la of the sheet 1 against the printing surface 4 whilst the sheet is moved to the second position, said device 5 will be referred to hereinafter as the holding-down means. The second abutment means 3 is arranged to be in opposing relationship with the holding-down means 5 and when the printing cylinder 4 is rotated in the direction of the arrow a, the abutment means 3 is arranged to co-act first with the free end 5a of the means 5 and to move said device against the leading edge la, said abutment means 3 being arranged to move not only the free end 5a of the holdingdown means but also the leading edge 1a of the sheet l to the register position R, as shown in FIG. 3.

The abutment means 3 is mounted to the cylinder 6 in a manner such as to enable said means to be withdrawn into and extended from the interior of the drum, and as soon as the abutment means 3 reaches the register position R, said means is withdrawn into the printing cylinder 4 by means not shown, at the same time as gripping means 6 are caused to co-act with the leading edge la of the sheet 1 to then commence rotation of the printing cylinder in the direction of the arrow b, i.e. to commence a printing sequence. Prior to this, the holding-down means 5 and the first abutment means 2 are rotated by means not shown away from the printing surface 4, to permit free passage of the sheet 1 beneath said means.

FIG. 5 shows diagramatically and in perspective part of a printing apparatus constructed in accordance with the invention, the sheet 1 being shown in the position shown in FIG. 2. In FIG. 5, the leading edge 1a of the sheet 1 is shown abutting two first abutment means 2 each of which is located on its respective side of the printing cylinder 4. Immediately adjacent the two first abutment means 2 are holding-down means 5, which are arranged to hold the leading edge la against the printing cylinder 4. Abutment means 3 are located immediately upstream of the holding-down means 5 as seen in the direction of forward movement of the sheet and, as will be seen from FIG. 5, upon further movement of the printing cylinder 4 in the direction of the arrow a the abutment means 3 will strike the free end 5a of the holding-down means.

The first abutment means 2 are securely connected to a pivotable pin 8 (FIG. 2) which extends through pairs of bearings 81, 82, which in turn are securely connected to a main part or a common part 7. The holdingdown means 5 are rotatably connected to the pin 8. By means of dogs 20 having the form of pins located on respective first abutment means 2, adjacent holdingdown means can be lifted from their co-acting position with the leading edge 1a of the sheet 1 at the same time as the first abutment means 2 are rotated up, to free the movement path of the sheet 1 when said sheet is retained against the printing surface 4 by said gripping devices. Respective dogs 20 are securely connected to the first abutment means 2 and extend beneath adjacent holding-down means. It should be mentioned that the gripping devices 6 have been omitted from FIG. 5 for the sake of clarity.

A first embodiment of the holding-down means 5 of the present invention is illustrated in side view in FIG.

6 and comprise a planar portion which narrows towards said free end 5a. The planar portion 5 extends slightly into the portion 8 and is retained there by an angle lever 5b.'The angle lever 5b extends through a recess 8a in said part 8 and into a groove 8b which serves as a guide for the planar portion 5. The free end 5a of the holding-down means is biased to the left in FIG. 6 by means of a spring 9, the movement 'of said free end being stopped by a wall portion 80. When the abutment means 3 presses against the free end 5a of the holdingdown means, the planar portion 5 is moved into the part 8 against the action of the spring 9. As soon as the abutment means 3 ceases to act on the free end 5a, the holding-down means is moved by said springs 9 to the position shown in FIG. 6.

The part 8 has a slide surface 8d arranged to co-act with the planar portion-of the holding-down means 5, to enable reciprocatory movement of said means. The

part 8 is capable of being rotated around the pin 8' in the manner illustrated and described with reference to FIG. 4. The holding-down means and the first abutment means 2 co-act with the same pin 8'.

In certain cases it may be desired to regulate the pressure of the holding-down means against the leading edge la of the sheet 1, and to this end there may be provided a further spring which is arranged to co-act with the part 8 and with a fixed part 7. The spring 10 may be made adjustable in a known manner, thereby to enable the force at which the holding-down means forces the leading edge of the sheet 1 against the cylinder surface to be adjusted.

With the illustrated embodiment, the first setting of the sheet is determined by the first abutment means 2. These abutment means are offset with respect to the abutment means 3, which is a necessary condition for the functioning of the aforedescribed arrangement. This arrangement has the disadvantage whereby the first position of alignment of the sheet is controlled by portions of the sheet edge different to those which con trol the second position of alignment of said sheet or register position. This is particularly true with sheets having an uneven edge surface. One solution to this problem would be to use the same sheet edge portions for both positions of alignment.

FIG. 7 is a side view of a further embodiment of a holding-down means according to the invention, said means supporting means for the first position of alignment. with this embodiment, the free end 5a of the holding-down means 5 is securely connected to the pin 8' (FIG. 6) and is able to adopt any one of three different positions. The first of these positions is shown in FIG. 7 in full lines, the second position is shown in FIG. 7 with dash-lines and the third position is shown when both the holding-down means and the first abutment means 2 adopt a position in which the sheet is released. The first abutment means 2 comprise a plate, the upper portion of which is held to the holding-down means 5 by means of a flat spring 21 or the like via a rivet 22. The spring 21 is also inteded to guide and to stiffen, the first abutment means 2.

In the first position, the first abutment means engages the cylindrical surface 4 and contributes toward the leading edge la of the sheet 1 obtaining a correct first alignment. Upon rotation of the pin 8' (not shown in FIG. 7) the free end 5a of the holding-down means is moved down into abutment with the leading edge la of the sheet, the second position. The first abutment means 2 are now pressed slightly harder against the surface 4. In the second position, the abutment means 3 on the printing cylinder will engage the abutment means 2 and move the leading edge 1a of the sheet 1, the first abutment means 2 and the holding-down means 5 rearwardly until the sheet 1 is located in the register position. Gripping means are then activated at the same time as the abutment means 3 is moved down in the printing cylinder and the holding-down means 5 together with the abutment means 2 are rotated up to release the sheet 1.

It should be noted that the free end 5a of the holdingdown means 5 serves to stiffen the leading edge In of the sheet 1 and to stiffen the abutment means 2 when said means are moved together with the holding-down means 5.

What is claimed is:

l. A printing apparatus in which the leading edge of a sheet to be printed upon is allotted a first position relative to a printing surface, from which position the sheet is arranged to be moved slightly rearwardly by a first abutment means to a second position or a register postion relative to said surface, wherein said leading edge is arranged to be held against said surface by one or more holding-down means having free ends which are arranged to register with or to extend beyond the leading edge of the sheet when said sheet is located in said first position, and wherein said abutment means is arranged to move the holding-down means and the leading edge of said sheet to said register position.

2. A printing apparatus as claimed in claim 1, wherein the holding-down means is movable against the action of a first spring.

3. A printing apparatus as claimed in claim 1, wherein the holding-down means is arranged to be held against the leading edge of the sheet by means of a regulatable force.

4. A printing apparatus according to claim 1, wherein a second abutment means for aligning said leading edge in a first position, and said holding-down means are connected to a rotatable pin, wherein gripping means are arranged for gripping said sheet, and wherein said pin, upon being rotated, is arranged to cause release of the sheet when said gripping means grip said sheet. i

5. A printing apparatus as claimed in claim 4, wherein said second abutment means are securely connected to said pin, wherein the holding-down means is pivotally connected to said pin, and wherein rotation of said pin also causes rotation of said holding-down means, via a dog securely connected to said second abutment means.

6. A printing apparatus according to claim 1, wherein the holding-down means carries an abutment shoulder.

7. A printing apparatus according to claim 6, wherein the abutment shoulder is connected to the holdingdown means via a spring or the like.

8. A printing apparatus according to claim 6, wherein the holding-down means is securely connected to a shaft.

9. A printing apparatus according to claim 6, wherein the holding-down means and the second abutment means are both arranged to be moved to the register position together with the sheet. 

1. A printing apparatus in which the leading edge of a sheet to be printed upon is allotted a first position relative to a printing surface, from which position the sheet is arranged to be moved slightly rearwardly by a first abutment means to a second position or a register postion relative to said surface, wherein said leading edge is arranged to be held against said surface by one or more holding-down means having free ends which are arranged to register with or to extend beyond the leading edge of the sheet when said sheet is located in said first position, and wherein said abutment means is arranged to move the holding-down means and the leading edge of said sheet to said register position.
 2. A printing apparatus as claimed in claim 1, wherein the holding-down means is movable against the action of a first spring.
 3. A printing apparatus as claimed in claim 1, wherein the holding-down means is arranged to be held against the leading edge of the sheet by means of a regulatable force.
 4. A printing apparatus according to claim 1, wherein a second abutment means for aligning said leading edge in a first position, and said holding-down means are connected to a rotatable pin, wherein gripping means are arranged for gripping said sheet, and wherein said pin, upon being rotated, is arranged to cause release of the sheet when said gripping means grip said sheet.
 5. A printing apparatus as claimed in claim 4, wherein said second abutment means are securely connected to saiD pin, wherein the holding-down means is pivotally connected to said pin, and wherein rotation of said pin also causes rotation of said holding-down means, via a dog securely connected to said second abutment means.
 6. A printing apparatus according to claim 1, wherein the holding-down means carries an abutment shoulder.
 7. A printing apparatus according to claim 6, wherein the abutment shoulder is connected to the holding-down means via a spring or the like.
 8. A printing apparatus according to claim 6, wherein the holding-down means is securely connected to a shaft.
 9. A printing apparatus according to claim 6, wherein the holding-down means and the second abutment means are both arranged to be moved to the register position together with the sheet. 